Antistatic photographic film



Nov. 29, 1955 v D. R. MOREY 2,725,297

ANTISTATIC PHOTOGRAPHIC FILM Fi led Oct. 8, 1952 u EMULSION A. ANTI-STATIC LAYER CONTAIN/N6 OELAT/N,

, WATER-SOLUBLE POLYMER/O SALT, ANO

WAT E R-SOLUBLE SIMPLE INORGANIC SALT DONALD R. MORE) IN VEN TOR.

ATTORNEYS United States .Ratent AN TISTATIC PHOTOGRAPHIC FILM Donaldv R. Morey, Rochester, N. Y.,- assignor to-.Eastman Kodak Company, Rochester, N. Y.,. a corporation of New Jersey Application October 8, 1952, Serial No. 313,771

6 Claims. (Cl. 959) This invention relatesto photographic ;film and particularly to a film protected against static.

The accumulation of electrical charges on photographic tested as irregular fogged patterns in the emulsion of the filnr after it .has been developed. Thesezstatic effects are particularly noticeable in films provided with. cellulose 1 nitrate supports, although they. are. .also evident on cel- ,lulose acetate supports, pa'rticularly-sincerzthe.adventrof high speed emulsions. Static markings on film are thought to. result also upon separation of emulsion. from paper during unwinding of a stockroll when the roll. was wound -,at.a humidity sutficiently high to-irnpart sticking.

Attempts have been made to'overcome :static in photographic-film by the application of' various layers tosthe i film support. 'materials designed to dissipate the electric chargesby providinghthe film with a conductingrsurface. 1 Materials These layers have in general. consistedof which absorb moisture and thereforenprovide, a conducting surfacehave frequently been employed. :Most of these methods have not proven entirely satisfactory with the newer high speed emulsions.

It is also known that antistatic layers-may be; made by adding to gelatin certain ionic .organiczmaterialsincluding water-soluble polymeric materials as described in Morey and White U. S. 'Patent. 2,639,234. Thepusexof water-soluble inorganic acid salts .in antistatic layers:.has also been proposed. None of these types ofantistatic rcoating has, however, been broadlysatisfa'ctory.for. all' of -the different film types whichnare manufactured.

It is therefore an object of the present invention to provide a-novel and efiectivemeans of protecting a sensitive photographic-film against static. -A furtherrobject isto provide a method of coating a photographic film in order to reduce its static tendency. -A stillfurther bje'ct-is to provide a suitable means for protecting cellulose acetate films especially cellulose .triacetate-films against static. producing photographic film of. considerably lowenelec- 'trical resistance while, at .the same time,- retainingits A further object is; to provide means 'of optical transparency. Other objects will 'appear'fromthe following description of my invention.

Theseobjects .are accomplished bycoating photographic film base with a mixture of three components: (1) gelatin, (2) a water-soluble polymeric, salt, and (3) a water- -soluble simple inorganic acid salt.

The accompanying drawing shows. a sectional view of 'film constructed according to-my invention.

'The ternary mixture of gelatin, water solublegpolyrneric :salt, .andvwater-soluble simple inorganic acidtsaltwhich "I proposeitonse produces an enhancedconductivi-ty:over

that of the sum of the separate components. There is Patented "Nov. 29, 1 9

afimarked-synergistic effect -ofthe' mixture which enables thedesired conductance level to be reached without having. tohave excessive amounts of-addenda which would otherwise lead .to incompatibilityanda hazy or sticky coating.

It has been found possible to add-sufi'icient'of these addenda to bring the surface resistivity below 10 ohms, a value which is sufficient to alleviate difiiculties from static electricity generated in the normal handling of the film. The surface resistance of the-usual gelatin backing is 50 to 100 times the value stated-above.

The surface resistivity was measured placing two parallel electrodes on the film at a fixed relative humidity of 50%; these electrodes are long compared to the distance between them, so as to avoid end effects. The observed resistance reading is divided 'by" the distance between electrodes and multiplied by their length, to obtain the surface resistivity.

' The ternary mixtures which I propose to use contain the following ingredients:

1. Gelatin. 2. Water-soluble polymeric salt, e. g.;

Carboxy methyl cellulose (sodium salt). Sodium alginate. Sodium cellulose sulfate. Cellulose acetate sodium sulfate. Methyl methacrylate methacrylic acid (sodium salt). Sulfonated polystyrene (sodium salt). Sodium polyethylene glycol lauroyl sulfate. 3. Water-soluble, simple. inorganic acid salt, e. g. sodium chloride.

When used to preventstatic on sensitive photographic film the mixtures of my invention may beincorporated in the. sensitive emulsion layer in. an..overcoating layer or used as a backing layer. Our agents possess such physical properties that when applied to the back of a cellulose ester film they form a cleartransparent layer on the film without any undesirable physical or photographic efiects. It is, of course, assumed that the'addenda willbe properly chosen or purified so that they have no fogging or desensitizing action upon light-sensitive emulsions. Our ternary mixtures are preferably applied to the back of the film, that is, to the side opposite that of the sensitive emulsion layer.

- The following examplesillustratemethods of applying the ternary mixturetofilms according to my invention.

Example 1 To an .aqueous. gelatin.solutioncontaining 5%: of

. gelatinthere was. added.20%' ofv the weight of thetgelatin of the sodium .salt .of carboxyme'thyl cellulose and. 2%

halide emulsion. This film showed good optical appear ance-of the backing. Films similarly coatedwith gelatin alone -and-with gelatin plus 20% of the-weight'ofthe gelatin of the-sodium salt of 'carboxymethyl cellulose and .with gelatin plus 2%of'the'weight ofgelatin'of sodium chloride were-brought to equilibrium with"50'% relative humidity and tested for electrical conductance. (in computing the'sum of the separate cor'iductances, the value for the gelatin check coating was subtractedpsincesgelatin would otherwisenbeuaddedtwice, i. e. with, the ..sodium chloride. .and .with. the. polymerusalt.) "The: following. re-

sults for electrical conductance were ObtainedKinthe tables, the value for ohms is the reciprocal ohms reading):

' l/RXlO ohms Gelatin check coating 0.069 Gelatin+20 percent Na salt of carboxymethyl cellulose 3.23 Gelatin-#2 percent NaCl 0.38 Sum of separate conductances of the components 3.54 Gelatin+20 percent CMC+2 percent NaCl 8.33

A synergistic factor of over 2 was obtained. Similar tests were made using other polymer salts with the following results.

Example 2 Ohms Gelatin check coating 0.011 Gelatin+20 percent sodium alginate 1.47 Gelatin+2 percent NaCl 0.141

Sum of separate conductances of the components 1.60 Gelatin+20 percent Na alginate-i-Z percent NaCl 6.25

A synergistic factor of nearly 4 was obtained.

Example 3 Ohms Gelatin check coating 0.014 Gelatin+10 percent sodium cellulose sulfate 0.045 Gelatin+2 percent NaCl 0.068

Sum of separate conductances of the components 0.099 Gelatin-H percent sodium cellulose sulfate+2 percent NaCl 0.217

A synergistic factor of 2 was obtained.

Example 4 Ohms Gelatin check coating as 0.014 Gelatin+20 percent sodium cellulose sulfate a- 0.061 Gelatin+2 percent NaCl 0.068

Sum of separate conductances of the components 0.115 Gelatin-l-ZO percent sodium cellulose sulfate+2 percent NaCl 0.333

A synergistic factor of 3 was obtained.

Gelatin-{-20 percent copolymer+4 percent NaCL- 125.

A synergistic factor of 26 was obtained.

Example 7 4 Ohms Gelatin check coating 0.01 Gelatin-F20 percent Na salt of sulfonated polystyrene 0.18 Gelatin-l-Z percent NaCl 0.1

Sum of separate conductances of the components 0.27 Gelatin-[-20 percent sulfonated polystyrene-l-Z percent Nam A synergistic factor of 4 was obtained.

In my coatings as finally dried, the gelatin should comprise at least 75% by weight of the ternary mixture;

the water-soluble polymeric salt should comprise between about 5 and 20% or slightly more, of the weight of the gelatin and the simple inorganic acid salt should comprise from about 2 to 10% or slightly more, of the weight of the gelatin.

In the accompanying drawing,

The single figure is a sectional view of a film constructed according to my invention. As shown therein, a suitably subbed film support 5.0 of any appropriate film base material such as cellulose acetate has coated thereon a gelatin-silver halide emulsion 111 and on the opposite side a layer 12 of gelatin, water-soluble polymeric salt and Water-soluble simple inorganic acid salt.

It will be understood that my invention is capable of numerous modifications within the scope of the appended claims.

I claim:

1. An antistatic photographic film comprising a cellulose ester support having thereon a sensitive silver halide emulsion layer and in one of the layers of the film a mixture of (l) gelatin, (2) a water-soluble polymeric salt selected from the group consisting of Water-soluble salts of carboxymethyl cellulose, alginic acid, cellulose acid sulfate, cellulose acetate acid sulfate, methyl methacrylate-methacrylic acid, sulfonated polystyrene and polyethylene glycol lauroyl acid sulfate, and (3) from about 2% to 10% of the weight of gelatin of sodium chloride, said gelatin comprising at least 75 by weight of said mixture.

2. An antistatic photographic film comprising a cellu lose ester support having one one side thereon a sensitive silver halide emulsion layer, and on the opposite side thereof a layer comprising a mixture of gelatin, the sodium salt of carboxymethyl cellulose, and from about 2% to 10% of the Weight of gelatin of sodium chloride, said gelatin comprising at least 75 of saidmixture.

3. An antistatic photographic film comprising a cellulose ester support having on one side tiereon a sensitive silver halide emulsion layer, and on the opposite side thereof a layer comprising a mixture of gelatin, sodium alginate, and from about 2% to 10% of the weight of gelatin of sodium chloride, said gelatin comprising at least 75 of said mixture.

4. An antistatic photographic film comprising a cellulose ester support having on one side thereon a sensitive silver halide emulsion layer, and on the opposite side thereof a layer comprising a mixture of gelatin, sodium cellulose sulfate, and from about 2% to 10% of the Weight of gelatin of sodium chloride, said gelatin comprising at least 75 of said mixture.

5. An antistatic photographic film comprising a cellulose ester support having on one side thereon a sensitive silver halide emulsion layer, and on the opposite side thereof a layer comprising a mixture of gelatin, cellulose acetate sodium sulfate, and from about 2% to 10% of the Weight of gelatin of sodium chloride, said gelatin comprising at least 75 of said mixture.

6. An antistatic photographic film comprising a cellulose ester support having on one side thereon a sensitive silver halide emulsion layer, and on the opposite side thereof a layer comprising a mixture of gelatin, the sodium salt of methyl-methacrylate-methacrylic acid, and from about 2% to 10% of the weight of gelatin of sodium chloride, said gelatin comprising at least 75% of said mixture.

References Cited in the file of this patent UNITED STATES PATENTS 1,981,102 Hagedorn et al. Nov. 20, 1934 2,118,059 Slack et a1. May 24, 1938 2,127,621 Staud et a1 Aug. 23, 1938 2,322,085 Yutzy June 15, 1943 2,357,590 Iatfe Sept. 5, 1944 2,386,167 Murray Oct. 2, 1945 

1. AN ANTISTATIC PHOTOGRAPHIC FILM COMPRISING A CELLULOSE ESTER SUPPORT HAVING THEREON A SENSITIVE SILVER HALIDE EMULSION LAYER AND IN ONE OF THE LAYERS OF THE FILM A MIXTURE OF (1) GELATIN, (2) A WATER-SOLUBLE POLYMERIC SALT SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE SALTS OF CARBOXYMETHYL CELLULOSE, ALGINIC ACID, CELLULOSE ACID SULFATE, CELLULOSE ACETATE ACID SULFATE, METHYL METHACRYLATE-METHACRYLIC ACID, SULFONATED POLYSTYRENE AND POLYETHYLENE GLYCOL LAUROYL ACID SULFATE, AND (3) FROM ABOUT 2% TO 10% OF THE WEIGHT OF GELATIN OF SODIUM CHLORIDE, SAID GELATIN COMPRISING AT LEAST 75% BY WEIGHT OF SAID MIXTURE. 